The present invention relates to an image data communicating apparatus and a communication data quantity adjusting method used in an image data communication system suitable for used when image data such as video images or the like is transferred in a network environment.
In an office network such as LAN, a Local Area Network, which is a computer network located mainly in one office, WAN, a Wide Area Network which is a computer network in which LANs located in a wider area are connected to each other, or the like, data can be exchanged between computers as terminals accommodated by the network.
Using the above LAN or WAN, there appeared in recent years an image data communication system in which a video camera, for example, is connected to a computer accommodated by the network, whereby image data such as video images may be exchanged among several computers.
FIG. 54 is block diagram showing a general image data communication system. In FIG. 54, reference numerals 101 and 102 denote computers. These computers 101 and 102 are accommodated by a network 103 such as LAN, WAN, or the like.
A video camera 104 generating video image data is connected to the computer 101, whereas a display 105 displaying image data thereon is connected to the computer 102. Reference numeral 106 denotes another computer transmitting/receiving data excepting image data.
The image data generated by the video camera 104 is transmitted from the computer 101 to the computer 102 over the network 103. When receiving the image data from the computer 101, the computer 102 controls and displays the received imaged data on the display 105.
A video image inputted from the above video camera 104 is constituted of a pluality of pictures which slightly differ from each other, each of which is called a frame. In the computer 101, the number of frames transmitted for a predetermined time period can be arbitrarily set. In particular, if the number of frames transmitted for a predetermined period increases, it is possible to smoothly display video image data.
However, the user on the transmitting side arbitrarily sets the number of frames without giving regard to the traffic of the network 103. Thus, the computer 101 on the transmitting side sends out data, as much as possible, to the network 103 even in a state where the network 103 is congested.
If the computers 101 and 102 process frames from the video camera 104 in the above general image data communication system shown in FIG. 54, data size of one frame constituting image data reaches an enormous size.
Particularly, if the user sets the number of transmitting frames for a predetermined period to a large number when image data is transmitted over the network 103 on a slow line in a degree of, for example, 64/56 kbps, a large part of the traffic of the network 103 is used for transfer of the image data, which disturbs smooth implementation of other service provided by the network 103.
Japanese Patent Laid-Open Publication No. 06-233139 discloses a technique in terms of an image transferring apparatus which calculates a transmission period from the data quantity accumulated when image data is transferred, and alters a compression rate of image data if the transmission period is judged to be longer than a desired transmission time so as to realize the desired transmission period as a result.
The above technique disclosed in Japanese Patent Laid-Open Publication No. 06-2333139, however, cannot transfer image data based on the traffic of a network. If the network is congested, it is impossible to smoothly carry out services other than the image transfer, similarly to the above case.
Japanese Patent Laid-Open Publication No. 07-95418 discloses a technique in terms of an image communication apparatus in which various parameters, used in the event of image transfer, can be manually set when the image is transferred.
The above technique disclosed in the Japanese Patent Laid-Open Publication No. 07-95418 has a disadvantage that the user cannot recognize the traffic of a network during image data communication. In consequence, the user cannot set parameters during image transfer according to a change in traffic of the network. As a result, similarly to the above case, it is impossible to smoothly carry out services other than image transfer if the network is congested.
Japanese Patent Laid-Open Publication No. 07-75092 discloses a technique in terms of a digital motion picture compressing technique which shifts high frequency components of motion picture data having been compressed to lower frequency components depending on the state of traffic when the motion picture data is transferred to control the quantity of transmission data, thereby ensuring the number of frames per unit time period.
The above technique disclosed in Japanese Patent Laid-Open Publication No. 07-75092, however, needs some means for more effectively transferring the motion picture data on the basis of the state of the traffic, since the motion picture data is compressed, moreover, a frequency of which is converted.
In light of the above problems, an object of the present invention is to provide an image data communicating apparatus and a communication data quantity adjusting method used in an image data communication system, which transfer image data in an appropriate quantity of data on the basis of the traffic of a network without affecting other service provided by the network.